Method and apparatus for optimizing redundant critical control systems

ABSTRACT

A method and system for determining a configuration of a redundant critical control system is provided. The method includes receiving power distribution system operating characteristic information, using a computer, determining a plurality of alternative configurations of the power distribution system that are consistent with the operating characteristic information and determining efficiency characteristics of each of the alternative configurations, and selecting a configuration from the plurality of alternative configurations. The system includes a computer system configured to receive power distribution system operating characteristic information, determine a plurality of alternative configurations of the power distribution system that are consistent with the operating characteristic information and determine life-cycle cost characteristics of each of the alternative configurations, and select a configuration from the plurality of alternative configurations.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is related to U.S. Patent Application No. 60/359,544 filed on Feb. 25, 2002 for “Integrated Protection, Monitoring, and Control” the content of which is incorporated in its entirety herein by reference. This application is also related to U.S. Patent Application No. 60/438,159 filed on Jan. 6, 2003 for “Single Processor Concept for Protection and Control of Circuit Breakers in Low-Voltage Switchgear” the content of which is incorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to electrical switchgear and more particularly, to a method and apparatus for facilitating maximizing a power distribution system reliability and system availability through optimizing power distribution system component redundancy and configuration.

[0003] In an industrial power distribution system, power generated by a power generation company may be supplied to an industrial or commercial facility wherein the power may be distributed throughout the industrial or commercial facility to various equipment such as, for example, motors, welding machinery, computers, heaters, lighting, and other electrical equipment. At least some known power distribution systems include switchgear which facilitates dividing the power into branch circuits which supply power to various portions of the industrial facility. Circuit breakers are provided in each branch circuit to facilitate protecting equipment within the branch circuit. Additionally, circuit breakers in each branch circuit can facilitate minimizing equipment failures since specific loads may be energized or de-energized without affecting other loads, thus creating increased efficiencies, and reduced operating and manufacturing costs. Similar switchgear may also be used within an electric utility transmission system and a plurality of distribution substations, although the switching operations used may be more complex.

[0004] Switchgear typically include multiple devices, other than the power distribution system components, to facilitate providing protection, monitoring, and control of the power distribution system components. For example, at least some known breakers include a plurality of shunt trip circuits, under-voltage relays, trip units, and a plurality of auxiliary switches that close the breaker in the event of an undesired interruption or fluctuation in the power supplied to the power distribution components. Additionally, at least one known power distribution system also includes a monitor device that monitors a performance of the power distribution system, a control device that controls an operation of the power distribution system, and a protection device that initiates a protective response when the protection device is activated.

[0005] In at least some other known power distribution systems, a monitor and control system operates independently of the protective system. For example, a protective device may de-energize a portion of the power distribution system based on its own predetermined operating limits, without the monitoring devices recording the event. The failure of the monitoring system to record the system shutdown may mislead an operator to believe that an over-current condition has not occurred within the power distribution system, and as such, a proper corrective action may not be initiated by the operator. Additionally, a protective device, i.e. a circuit breaker, may open because of an over-current condition in the power distribution system, but the control system may interpret the over-current condition as a loss of power from the power source, rather than a fault condition. As such, the control logic may undesirably attempt to connect the faulted circuit to an alternate source, thereby restoring the over-current condition. In addition to the potential increase in operational defects which may occur using such devices, the use of multiple devices and interconnecting wiring associated with the devices may cause an increase in equipment size, an increase in the complexity of wiring the devices, and/or an increase in a quantity of devices installed.

BRIEF DESCRIPTION OF THE INVENTION

[0006] In one aspect, a method for determining a configuration of a redundant critical control system is provided. The method includes receiving power distribution system operating characteristic information, using a computer, determining a plurality of alternative configurations of the power distribution system that are consistent with the operating characteristic information and determining efficiency characteristics of each of the alternative configurations, and selecting a configuration from the plurality of alternative configurations.

[0007] In another aspect, a computer system for determining a configuration of a redundant critical control system is provided. The computer system is configured to receive power distribution system operating characteristic information, determine a plurality of alternative configurations of the power distribution system that are consistent with the operating characteristic information and determining efficiency characteristics of each of the alternative configurations, and select a configuration from the plurality of alternative configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is an exemplary schematic illustration of a power distribution system;

[0009]FIG. 2 is an exemplary schematic illustration of a node power system;

[0010]FIG. 3 is an exemplary schematic illustration of a central control processing unit that may used with the power distribution system shown in FIG. 1;

[0011]FIG. 4 is an exemplary schematic illustration of a node electronic unit that may used with the power distribution system shown in FIG. 1;

[0012]FIG. 5 is an exemplary schematic illustration of a circuit breaker that may used with the power distribution system shown in FIG. 1;

[0013]FIG. 6 is a simplified block diagram of a power distribution system design computer system that may be used with power distribution system 10 shown in FIG. 1;

[0014]FIG. 7 is an expanded version block diagram of an exemplary embodiment of a server architecture of power distribution system design computer system shown in FIG. 6;

[0015]FIG. 8 is a flow chart illustrating an exemplary embodiment of a method for operating power distribution system shown in FIG. 1;

[0016]FIG. 9 is a flow chart illustrating an exemplary embodiment of a method 900 optimizing a reliability of a plurality of control power sources in the power distribution system shown in FIG. 1;

[0017]FIG. 10 is a flow chart illustrating an exemplary embodiment of a method for determining a probability that a power distribution system circuit breaker error will not affect the reliability of the power distribution system shown in FIG. 1; and

[0018]FIG. 11 is a flow chart illustrating an exemplary embodiment of a method for operating power distribution system shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0019]FIG. 1 illustrates an exemplary schematic illustration of a power distribution system 10, used by an industrial facility for example. In an exemplary embodiment, system 10 includes at least one main feed system 12, a power distribution bus 14, a plurality of power circuit switches or interrupters, also referred to herein as a circuit breakers (CB) 16, and at least one load 18, such as, but not limited to, motors, welding machinery, computers, heaters, lighting, and/or other electrical equipment.

[0020] In use, power is supplied to a main feed system 12, i.e. a switchboard for example, from a source (not shown) such as, an electric generator driven by a prime mover locally, or an electric utility source from an electrical substation. The prime mover may be powered from, for example, but not limited to, a turbine, or an internal combustion engine. Power supplied to main feed system 12 is divided into a plurality of branch circuits by a plurality of busbars configured to route the power from a branch feed breaker and a bus-tie breaker to a plurality of load circuit breakers 16 which supply power to various loads 18 in the industrial facility. In addition, circuit breakers 16 are provided in each branch circuit to facilitate protecting equipment, i.e. loads 18, connected within the respective branch circuit. Additionally, circuit breakers 16 facilitate minimizing equipment failures since specific loads 18 may be energized or de-energized without affecting other loads 18, thus creating increased efficiencies, and reduced operating and manufacturing costs.

[0021] Power distribution system 10 includes a circuit breaker control protection system 19 that includes a plurality of node electronics units 20 that are each electrically coupled to a digital network 22. Circuit breaker control protection system 19 also includes at least one central control processing unit (CCPU) 24 that is electrically coupled to digital network 22 via a switch 23 such as, but not limited to, an Ethernet switch 23. In use, each respective node electronics unit 20 is electrically coupled to a respective circuit breaker 16, such that CCPU 24 is electrically coupled to each circuit breaker 16 through digital network 22 and through an associated node electronics unit 20.

[0022] In one embodiment, digital network 22 includes, for example, at least one of a local area network (LAN) or a wide area network (WAN), dial-in-connections, cable modems, and special high-speed ISDN lines. Digital network 22 also includes any device capable of interconnecting to the Internet including a web-based phone, personal digital assistant (PDA), or other web-based connectable equipment.

[0023] In one embodiment, CCPU 24 is a computer and includes a device 26, for example, a floppy disk drive or CD-ROM drive, to facilitate reading instructions and/or data from a computer-readable medium 28, such as a floppy disk or CD-ROM. In another embodiment, CCPU 24 executes instructions stored in firmware (not shown). CCPU 24 is programmed to perform functions described herein, but other programmable circuits can likewise be programmed. Accordingly, as used herein, the term computer is not limited to just those integrated circuits referred to in the art as computers, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits, and other programmable circuits. Additionally, although described in a power distribution setting, it is contemplated that the benefits of the invention accrue to all electrical distribution systems including industrial systems such as, for example, but not limited to, an electrical distribution system installed in an office building.

[0024]FIG. 2 is an exemplary schematic illustration of a node power distribution system 29 that can be used with power distribution system 10 (shown in FIG. 1) and more specifically, with circuit breaker control protection system 19 (shown in FIG. 1). Node power distribution system 29 includes a power source 30 that is electrically coupled to node electronic units 20 through a node power distribution bus 32. In an exemplary embodiment, power source 30 is an uninterruptible power supply (UPS). In one embodiment, power source 30 receives power from power distribution system 10 and then distributes this power to node electronic units 20 through node power distribution bus 32. In an alternative embodiment, power is not supplied to power source 30, but rather, power source 30 supplies power to node electronic units 20 using an internal power supply, such as, but not limited to, a plurality of batteries (not shown). In another alternate embodiment, node electronic units 20 are powered by secondary current available from current sensor 82 and/or voltage sensor 84. In this embodiment, circuit breaker control protection system 19 would not include node power distribution system 29, power source 30, or node power distribution bus 32.

[0025]FIG. 3 is an exemplary schematic illustration of CCPU 24. CCPU 24 includes at least one memory device 40, such as, but not limited to, a read only memory (ROM) 42, a flash memory 44, and/or a random access memory (RAM) 46. CCPU 24 also includes a central processor unit (CPU) 48 that is electrically coupled to at least one memory device 40, as well as an internal bus 50, a communications interface 52, and a communications processor 54. In an exemplary embodiment, CCPU 24 is a printed circuit board and includes a power supply 56 to supply power to a plurality of devices on the printed circuit board.

[0026] Additionally, in an exemplary embodiment, internal bus 50 includes an address bus, a data bus, and a control bus. In use, the address bus is configured to enable CPU 48 to address a plurality of internal memory locations or an input/output port, such as, but not limited to communications interface 52 through communications processor 54, and a gateway interface 58, through a gateway processor 56. The data bus is configured to transmit instructions and/or data between CPU 48 and at least one input/output, and the control bus is configured to transmit signals between the plurality of devices to facilitate ensuring that the devices are operating in synchronization. In the exemplary embodiment, internal bus 50 is a bi-directional bus such that signals can be transmitted in either direction on internal bus 50. CCPU 24 also includes at least one storage device 60 configured to store a plurality of information transmitted via internal bus 50.

[0027] In use, gateway interface 58 communicates to a remote workstation (not shown) via an Internet link 62 or an Intranet 62. In the exemplary embodiment, the remote workstation is a personal computer including a web browser. Although a single workstation is described, such functions as described herein can be performed at one of many personal computers coupled to gateway interface 58. For example, gateway interface 58 may be communicatively coupled to various individuals, including local operators and to third parties, e.g., remote system operators via an ISP Internet connection. The communication in the example embodiment is illustrated as being performed via the Internet, however, any other wide area network (WAN) type communication can be utilized in other embodiments, i.e., the systems and processes are not limited to being practiced via the Internet. In one embodiment, information is received at gateway interface 58 and transmitted to node electronics unit 20 via CCPU 24 and digital network 22. In another embodiment, information sent from node electronics unit 20 is received at communication interface 52 and transmitted to Internet 62 via gateway interface 58.

[0028]FIG. 4 is an exemplary schematic illustration of single node electronic unit 20. In the exemplary embodiment, node electronic unit 20 is a unitary device mounted remotely from CCPU 24 and circuit breaker 16. In an exemplary embodiment, node electronic unit 20 is separate from, but proximate to circuit breaker 16. In an exemplary embodiment, node electronic unit 20 is a printed circuit board.

[0029] In one embodiment, node electronics unit 20 receives signals input from a plurality of devices, such as, but not limited to, a current sensor 82, and a voltage sensor 84, and/or circuit breaker 16. Status input device 86 receives a plurality of status signals from circuit breaker 16 can include signals related to one or more conditions of the breaker, such as, but not limited to, an auxiliary switch status, and a spring charge switch status. Additionally, node electronics unit 20 sends signals 86 to at least circuit breaker 16 in order to control one or more states of the breaker.

[0030] In use, signals input from status input device 86, current sensor 82, and voltage sensor 84, are transmitted to CCPU 24 via node electronics unit 20, and digital network 22. Node electronics unit 20 receives the input from status input device 86, current sensor 82, and voltage sensor 84, and packages a digital message that includes the input and additional data relating to a health and status of node electronics unit 20. The health and status data may include information based on problems found by internal diagnostic routines and a status of self checking routines that run locally in node electronics unit 20. The data transmitted to CCPU 24 via node electronics unit 20 is processed by CCPU 24, which outputs a signal to node electronics unit 20 via digital network 22. In the exemplary embodiment, node electronics unit 20 actuates circuit breaker 16 in response to the signal received from CCPU 24. In one embodiment, circuit breaker 16 is actuated in response to commands sent only by CCPU 24, i.e., circuit breaker 16 is not controlled locally by node 20,but rather is operated remotely from CCPU 24 based on inputs received from current sensor 82, voltage sensor 84, and status inputs 86 received from node electronics unit 20 over network 22.

[0031]FIG. 5 is an exemplary schematic illustration of circuit breaker 16 that is electrically coupled to node electronics unit 20. In the exemplary embodiment, circuit breaker 16 includes a switch assembly that includes movable and/or stationary contacts, an arc suppression means, and a tripping and operating mechanism. Circuit breaker 16 auxiliaries include only a trip coil 100, a close coil 102, an auxiliary switch 104, a spring charge switch 106, and a motor 108. Circuit breaker 16 does not include a trip unit. Auxiliary switches and sensors are coupled to node electronics unit 20 through a standard wiring harness 110, which may include both copper wiring and communications conduits. Current sensor 82, and voltage sensor 84 are coupled to node electronics unit 20 through a cable 112 that may include copper wiring and/or communications conduits. Circuit breaker 16 is a unitary device mounted proximate to CCPU 20, current sensor 82, and voltage sensor 84. The various components of breaker 16 (e.g., trip coil 100, close coil 102, auxiliary switch 104, spring charge switch 106, motor 108) can be powered by node electronics unit 20. Alternately, breaker 16 can be powered by secondary current available from current sensor 82 and/or voltage sensor 84. Circuit breaker 16 is in electrical communication with node electronics unit 20 through a wiring harness 110 (not shown in FIG. 5), which may include copper wiring, communications conduits, and any combination thereof. Current sensor 82, and voltage sensor 84 are in electrical communication with node electronics unit 20 through a cable 112 (not shown in FIG. 5) that may include copper wiring, communications conduits, and any combination thereof.

[0032] In use, actuation signals from node electronics unit 20 are transmitted to circuit breaker 16 to actuate a plurality of functions in circuit breaker 16, such as, but not limited to, operating a trip coil 100, operating a close coil 102, and affecting a circuit breaker lockout feature. An auxiliary switch 104 and a spring charge switch 106 provide a status indication of circuit breaker parameters to node electronics unit 20. Motor 108 is configured to recharge a close spring (not shown) after circuit breaker 16 closes. It should be appreciated that the motor 108 can include, for example, a spring charge switch, a solenoid or any other electromechanical device capable of recharging a trip spring. To close circuit breaker 16, a close coil 102 is energized by a close signal from actuation power module 90. Close coil 102 actuates a closing mechanism (not shown) that couples at least one movable electrical contact (not shown) to a corresponding fixed electrical contact (not shown). The closing mechanism of circuit breaker 16 latches in a closed position such that when close coil 102 is de-energized, circuit breaker 16 remains closed. When breaker 16 closes, an “a” contact of auxiliary switch 104 also closes and a “b” contact of auxiliary switch 104 opens. The position of the “a” and “b” contacts is sensed by node electronics unit 20. To open circuit breaker 16, node electronics unit 20 energizes trip coil (TC) 100. TC 100 acts directly on circuit breaker 16 to release the latching mechanism that holds circuit breaker 16 closed. When the latching mechanism is released, circuit breaker 16 will open, opening the “a” contact and closing the “b” contact of auxiliary switch 104. Trip coil 100 is then de-energized by node electronics unit 20. After breaker 16 opens, with the close spring recharged by motor 108, circuit breaker 16 is prepared for a next operating cycle. In the exemplary embodiment, each node electronics unit 20 is coupled to circuit breaker 16 in a one-to-one correspondence. For example, each node electronics unit 20 communicates directly with only one circuit breaker 16. In an alternative embodiment, node electronics unit 20 may communicate with a plurality of circuit breakers 16.

[0033]FIG. 6 is a simplified block diagram of a power distribution system design computer system 600 including a server system 612 including a disk storage unit 613 for data storage, and a plurality of client sub-systems, also referred to as client systems 614, connected to server system 612. In one embodiment, client systems 614 are computers including a web browser, such that server system 612 is accessible to client systems 614 via the Internet. Client systems 614 are interconnected to the Internet through many interfaces including a network, such as a local area network (LAN) or a wide area network (WAN), dial-in-connections, cable modems and special high-speed ISDN lines. Client systems 614 could be any device capable of interconnecting to the Internet including a web-based phone, personal digital assistant (PDA), or other web-based connectable equipment. A database server 616 is connected to a database 618 containing information on a variety of matters, as described below in greater detail. In one embodiment, centralized database 618 is stored on server system 612 and can be accessed by potential users at one of client systems 614 by logging onto server system 612 through one of client systems 614. In an alternative embodiment database 618 is stored remotely from server system 612 and may be non-centralized.

[0034]FIG. 7 is an expanded version block diagram 700 of an example embodiment of a server architecture of power distribution system design computer system 100 shown in FIG. 6. Components in diagram 700, identical to components of system 600 (shown in FIG. 6), are identified in FIG. 7 using the same reference numerals as used in FIG. 6. System 700 includes server system 612 and client systems 614. Server system 612 further includes database server 616, an application server 722, a web server 723, a fax server 726, a directory server 728, and a mail server 730. Disk storage unit 732 is coupled to database server 616 and directory server 728. Servers 616, 722, 723, 726, 728, and 730 are coupled in a local area network (LAN) 734. In addition, a system administrator's workstation 738, a user workstation 740, and a supervisor's workstation 742 are coupled to LAN 734. Alternatively, workstations 738, 740, and 742 are coupled to LAN 734 via an Internet link or are connected through an Intranet.

[0035] Each workstation, 738, 740, and 742 is a personal computer having a web browser. Although the functions performed at the workstations typically are illustrated as being performed at respective workstations 738, 740, and 742, such functions can be performed at one of many personal computers coupled to LAN 734. Workstations 738, 740, and 742 are illustrated as being associated with separate functions only to facilitate an understanding of the different types of functions that can be performed by individuals having access to LAN 734. In an example embodiment, client system 614 includes a workstation 750 which can be used by an internal analyst or a designated outside field engineer to review power distribution system design information relating to a system.

[0036] Server system 612 is configured to be communicatively coupled to various individuals, including employee workstation 744 and to design engineer workstation 746 via an ISP Internet connection 748. The communication in the example embodiment is illustrated as being performed via the Internet, however, any other wide area network (WAN) type communication can be utilized in other embodiments, i.e., the systems and processes are not limited to being practiced via the Internet. In addition, and rather than WAN 736, local area network 734 could be used in place of WAN 736.

[0037] In the exemplary embodiment, any authorized individual having a workstation 744 can access power distribution system design computer system 600. At least one of the client systems includes a manager workstation 750 located at a remote location. Workstations 744 and 750 are personal computers having a web browser. Also, workstations 744 and 750 are configured to communicate with server system 612. Furthermore, fax server 726 communicates with remotely located client systems, including a client system 750 via a telephone link. Fax server 726 is configured to communicate with other client systems 738, 740, and 742 as well.

[0038]FIG. 8 is a flow chart illustrating an exemplary embodiment of a method 800 for operating power distribution system 10 shown in FIG. 1. Method 800 includes an algorithm that determines the redundancy level of each critical component in power distribution system 10. This algorithm is controlled by minimizing the life cycle cost, subjected to a system availability constraint. This availability constraint is for circuit breaker control protection system 19 to have a greater availability than that of current local control protection systems.

[0039] Failure rate prediction methods provide a tool with which components may be selected. A set of conditions in which the components operate, such as, the temperature or environmental conditions is defined. The prediction methodology carries out a failure rate calculation as defined by predetermined parameters selected based on known and desired performance goals. For example, components that make up power distribution system 10 can be defined in a tree structure. The tree may be composed entirely of components or it could be subdivided into blocks each of which could hold other blocks or components. In this way power distribution system 10 can easily be represented as a combination of system and subsystems. A failure rate model for each component is made up of a base failure rate for that particular type of component and multiplying factors that depend on the operating conditions experienced by the component.

[0040] Method 800 utilizes an optimization procedure that receives 802 a set of parameters that describe power distribution system 10. In one embodiment, the parameters include a number and/or reliability of available power sources, a number and/or configuration of branch circuits, a number and rating of a plurality of loads. The procedure then varies 804 the redundancy of each component in system 10 for a given set of parameters, while meeting predetermined requirements and expectations. The redundancy is limited to integer values only; thus resulting in realistic parameters that can be physically implemented. For each level of redundancy for each component, a power distribution system reliability is determined 806. An associated life cycle cost, reliability and availability of each level of redundancy is considered 808. A level of redundancy that yields an optimum level of redundancy for each component is determined 810 for the given set of parameters. In one embodiment used for circuit breaker control and protection system 19, the resulting architecture is doubly redundant in the various components that constitute the centralized control architecture. For the particular example considered, these included the CCPU 24, communication network 22, and the power supply connections. Some features include redundancy determined in view of optimizing an application dependent cost function. In one embodiment, the calculation is fast by using a programmed Excel file, in which a “solver” function is employed. Features also include the ability to have any number of requirements or limitations, as well as any number of items that can be redundant. The only portion that needs to be updated for each particular system is its layout.

[0041] Accordingly, an ability to provide quick results that are able to be physically and realistically implemented is provided. Thus, resulting in “true” optimizations within a short period of time. One advantage is the optimally determined redundant architecture. In addition, the calculation is rigorous, fast, and simple, resulting in a structure that is able to be physically & realistically implemented. Additionally, a quick and easy procedure for determining the optimal redundancy of a complex system for a given set of constraints is provided. For example, one implementation considered the constraints to include overall life cycle costs and the systems availability. This procedure resulted in a doubly redundant circuit breaker control protection system architecture.

[0042]FIG. 9 is a flow chart illustrating an exemplary embodiment of a method 900 for operating power distribution system 10 shown in FIG. 1. Method 900 facilitates optimizing a reliability of a plurality of control power sources in power distribution system 10. The control power sources supply, for example, node electronics units 20 with power to energize node electronic unit 20 circuits and drive node electronic unit 20 outputs. Method 900 begins by determining 902 a user reliability goal. In one embodiment, the reliability goal may be mandated by a customer preference. In another embodiment, the reliability goal may be determined 902 by applying known standards or specifications to system 10 design inputs. An analysis of the control power supply for circuit breaker control protection system 19 is performed. In this analysis, the control power is optimized to yield a customer's expected reliability, or reliability goal. A reliability of the facility's available power supplies is determined 904 individually. A reliability of various combinations of these power supplies is determined 906 based on the reliability of the individual power supplies. The determined reliability of the combinations of power supplies is compared 908 to the reliability goal. If the determined reliability does not meet the reliability goal, the algorithm determines 906 a reliability of a different combination of power supply combinations. If the determined 606 reliability meets the reliability goal, the algorithm outputs the combination of power supply so that it may be implemented 910. In the exemplary embodiment, the determined combination of available power supplies is implemented in the design phase of a new power distribution system 10. In another embodiment, system 10 implements 910 the determined 906 combination of power supplies by generating commands and actions to appropriate circuit breakers 16 to achieve the optimum lineup determined 906. In another embodiment, system 10 outputs recommended commands and actions for appropriate circuit breakers 16 for an operator to implement 910 to achieve the optimum lineup determined 906.

[0043] Accordingly, a designer is enabled to quickly and accurately configure what power supplies should be utilized for the critical control system, thus allowing for quicker design time than at least some other methods. Additionally, any unneeded power supply redundancy is eliminated, thus reducing the quantity of equipment needed, the maintenance that the equipment might require, the cost of supplying such equipment. One aspect includes an ability to determine what combination of the facilities available power supplies are needed to obtain the desired system reliability. This procedure enables this result to be obtained in a short period of time.

[0044]FIG. 10 is a flow chart illustrating an exemplary embodiment of a method 1000 for operating power distribution system 10 shown in FIG. 1. Method 1000 facilitates determining a probability that a circuit breaker error will not affect the power distribution system reliability. Because all power distribution system monitored parameters are available to CCPU 24 at all times, a circuit breaker error detected by CCPU 24 can be compensated for by reconfiguring the operation of circuit breakers 16 supplying power to the affected circuit breaker 16. Method 1000 includes detecting 1002 a circuit breaker 16 error in any of the circuit breaker in power distribution system 10. An error is defined as a power distribution system component malfunction that occurs when the protection features of power distribution system 10 are not needed. The protection features of power distribution system 10 are needed when a power line fault occurs. A power line fault is defined as a malfunction of the power delivery components of power distribution system 10 and loads 18, such as, for example, but, not limited to, instantaneous over current, short and long time over current, ground fault, differential fault, and under and over frequency. A system failure is defined as a component error that coincides with a line fault. In such a situation, the protection features of power distribution system 10 would be needed to clear the line fault but, because of a component error, the protection features may be unavailable. When a component error is detected 1002, power distribution system 10 responds by determining 1004 an alternative trip scheme for the affected circuit breaker 16 to enable clearing a fault, should one occur, necessitating operation of the affected circuit breaker 16. For example, in a hierarchical power system, a plurality of supply circuit breakers each supply power from a power source to a power distribution system. The supply circuit breakers may supply a distribution bus that includes switchgear, such as, a plurality of feeder breakers that each supply power to an electrical load. Each bus may also be coupled to other buses through a bus-tie breaker. The system as described is hierarchical in that each circuit breaker is supplied from another circuit breaker usually with a larger current carrying capability and usually supplying other circuit breaker as well. The supply circuit breaker usually has the largest current carrying capability whereas individual load circuit breaker usually have the lowest current carrying capability. After the circuit breakers that supply the affected circuit breaker are determined, the operation of the determined supply circuit breakers may be adjusted 1006. This may be done by adjusting 1008 trip curves for the supplying circuit breakers so that they will trip at a current level that will compensate for the loss of the affected breaker's functionality. Additionally, the global information set of power distribution system 10 electrical parameters may be used to calculate electrical parameters at the affected circuit breaker and a compensatory monitoring 1010 regime may be used to trip the determined supply circuit breakers to facilitate limiting current flow to the affected circuit breaker.

[0045]FIG. 11 is a flow chart illustrating an exemplary embodiment of a method 1100 for operating power distribution system 10 shown in FIG. 1. Method 1100 facilitates determining an optimized power distribution system 10 configuration based on a predetermined power distribution system 10 configuration modified to incorporate software considerations into the determination. As discussed above, a configuration of power distribution system 10 is determined using optimization techniques that include optimizing system component reliability based on a redundancy of critical components, an inherent failure probability of components, i.e. mean time between failures (MTBF), mean time to failure (MTTF), and mean time to repair (MTTR), optimizing system component availability, and optimizing total system reliability and availability. In one embodiment, MTBF, is defined as being equal to the sum of MTTF and MTTR. The MTTF for a component may be obtained by analyzing historical data or using standard prediction methods. Once an optimum configuration based on reliability, availability and cost is determined, an additional, constructability evaluation is conducted. Constructability optimizes component availability, manufacturing, and power distribution system maintenance considerations. Additionally, an optimum power distribution system may include a level of redundancy that complicates constructability disadvantageously, necessitating a further review of the determined power distribution system 10 configuration. One area of review is the software which will be controlling power distribution system 10. Software considerations for power distribution system 10 include the level of redundancy of the plurality of node electronics units 20, redundancy of network 22 and the redundancy of CCPU 24. For each level of redundancy software running on power distribution system 10 will manage communications and resolve conflicts. In one embodiment, conflict resolution solutions will use a safety priority resolution methodology. In another embodiment, software voting will resolve command conflicts in power distribution system 10. Latency considerations influence the conflict resolution solution determined.

[0046] Once an optimized hardware configuration of power distribution system 10 is determined, a corresponding software configuration is determined 1102. A cost to implement such a corresponding software configuration is determined 1104. The determination includes labor, schedule, production resource variables. The determined hardware configuration and the corresponding software configuration are varied 1106 to establish an optimum hardware configuration/software configuration solution. For each configuration variation, cost is evaluated 1108 based on at least one of schedule, resources, reliability, availability and labor. Schedule, resource, and labor cost may be interrelated in that shortening a production or design schedule may increase labor costs due to increased numbers of people performing the work in a shorter time span and increased overtime costs. Resource cost also includes an opportunity cost for alternative uses of resources. Reliability and availability costs include costs associated with redundancy, component quality, and testing costs. After each evaluation, the process iterates to a subsequent configuration and evaluated again.

[0047] The above-described power distribution systems are cost-effective and highly reliable. Each system includes a central control unit and networked devices to facilitate protecting a set of switchgear. Devices local to each circuit breaker monitor voltage and current signals from sensors located proximate each circuit breaker. The central control receives all monitored signals from all devices over the high-speed network. The central control implements protection and optimization algorithms for each breaker node based on global voltage and current signals. This method offers performance advantages over existing local, non-networked protection. In many overcurrent faults, the fault level may appear at multiple levels in the electrical protection hierarchy. Branch, feeder and main circuit breakers may all “see” the fault. Protection engineers can partially avoid the problem by setting longer delays. This results in faults at high levels in the hierarchy causing more damage and still can result in multiple devices interrupting, removing electrical service from circuits that do not have a fault. Additionally the system components and configuration are facilitated to be optimized to provide high reliability and high availability. Accordingly, power distribution system 10 facilitates protection and optimization of power system operation in a cost-effective and reliable manner.

[0048] Exemplary embodiments of power distribution system components are described above in detail. The components are not limited to the specific embodiments described herein, but rather, components of each system may be utilized independently and separately from other components described herein. Each power distribution system component can also be used in combination with other power distribution system components.

[0049] While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims. 

What is claimed is:
 1. A method for determining a configuration of a redundant critical control system, said method comprising: receiving power distribution system operating characteristic information; using a computer, determining a plurality of alternative configurations of the power distribution system that are consistent with the operating characteristic information and determining life-cycle cost characteristics of each of the alternative configurations; and selecting a configuration from the plurality of alternative configurations.
 2. A method in accordance with claim 1 wherein selecting a configuration comprises selecting a configuration that facilitates optimizing the power distribution system life-cycle cost of a plurality of components of the power distribution system.
 3. A method in accordance with claim 2 wherein selecting a configuration comprises selecting a configuration wherein life-cycle costs include at least one of initial procurement cost, installation cost, maintenance cost, and replacement cost.
 4. A method in accordance with claim 1 further comprises: receiving optimization criteria; and determining a system reliability and system availability of each of the alternative configurations based on the optimization criteria.
 5. A method in accordance with claim 4 further comprising selecting a configuration that facilitates optimizing the power distribution system reliability wherein the reliability is measured as a probability of the system functionality at a first time that is greater than or equal to the system functionality at a second time wherein the first time is later than the second time.
 6. A method in accordance with claim 4 further comprising selecting a configuration that facilitates optimizing the power distribution system availability wherein the availability is measured as a probability of the system functionality at any time is greater than or equal to a predetermined system functionality goal.
 7. A method in accordance with claim 1 wherein determining a plurality of alternative configurations of the power distribution system comprises varying a number of components in a redundant scheme for each alternative configuration.
 8. A method in accordance with claim 1 further comprising: receiving a set of parameters describing a plurality components of the power distribution system; varying a redundancy of the plurality components for the received set of parameters; and determining a power distribution system reliability and system availability for each level of redundancy.
 9. A method in accordance with claim 8 wherein varying a redundancy of the plurality of components comprises varying a redundancy of the plurality of components wherein the plurality of components includes at least one of a central control processing unit (CCPU), a CCPU communications interface, a digital communications network, an Ethernet switch, a node electronics unit (NEU), an uninterruptible power supply (UPS), a main power supply to the UPS, a communications connection, and a circuit breaker.
 10. A method in accordance with claim 8 further comprising: evaluating at least one of a life cycle cost, a system availability, and a system reliability for each level of redundancy; and determining a level of redundancy to facilitate optimizing the power distribution system life-cycle cost, reliability, and availability.
 11. A method in accordance with claim 8 wherein receiving a set of parameters comprises receiving a set of parameters that includes at least one of a number of available power sources, a reliability of available power sources, a number of branch circuits, a configuration of branch circuits, a number of a plurality of loads, and a rating of a plurality of loads.
 12. A method in accordance with claim 8 further comprising: determining a user's power distribution system reliability goal; determining a reliability of each available control power supply; determining a reliability of a plurality of combinations of each available control power supply; and comparing the reliability of each combination of available power supplies to the determined reliability goal.
 13. A method in accordance with claim 1 wherein the power distribution system includes at least one circuit breaker, each circuit breaker supplying a load with electrical power from at least one electrical source, the circuit breakers configured in a hierarchical format from load to source, said method further comprising: detecting a circuit breaker error associated with a first circuit breaker that prevents the first circuit breaker from interrupting a flow of load current; determining at least one alternate circuit breaker to interrupt the flow of load current; adjusting an operation of the determined at least one alternative circuit breaker.
 14. A method in accordance with claim 13 wherein adjusting an operation of the determined at least one alternative circuit breaker comprises modifying a trip curve of the determined at least one alternative circuit breaker.
 15. A method in accordance with claim 13 wherein adjusting an operation of the determined at least one alternative circuit breaker comprises inferring electrical parameters at the first circuit breaker based on electrical parameters sensed in the power distribution system.
 16. A method in accordance with claim 10 further comprising: determining a power distribution system software configuration corresponding to the determined level of redundancy; determining a cost of implementing the power distribution system software configuration; varying the determined level of redundancy; and determining the power distribution system software configuration that facilitates optimizing the power distribution system cost.
 17. A method in accordance with claim 16 wherein determining a cost of implementing the power distribution system software configuration comprises determining a cost of implementing the power distribution system software configuration wherein cost includes at least one of a production schedule cost, a resource cost, and a labor cost.
 18. A method in accordance with claim 16 wherein determining the power distribution system software configuration that facilitates optimizing the power distribution system cost comprises determining the power distribution system software configuration that facilitates optimizing the power distribution system cost wherein the power distribution system cost includes at least one of a production schedule cost, a resource cost, a labor cost, a reliability cost, and an availability cost.
 19. A computer system for determining a configuration of a redundant critical control system, said computer configured to: receive power distribution system operating characteristic information; determine a plurality of alternative configurations of the power distribution system that are consistent with the operating characteristic information and determine life-cycle cost characteristics of each of the alternative configurations; and select a configuration from the plurality of alternative configurations.
 20. A computer system in accordance with claim 19 configured to select a configuration that facilitates optimizing the power distribution system lifecycle cost of a plurality of components of the power distribution system.
 21. A computer system in accordance with claim 20 configured to select a configuration wherein life-cycle costs include at least one of initial procurement cost, installation cost, maintenance cost, and replacement cost.
 22. A computer system in accordance with claim 19 further configured to: receive optimization criteria; and determine a system reliability and system availability of each of the alternative configurations based on the optimization criteria.
 23. A computer system in accordance with claim 22 further configured to select a configuration that facilitates optimizing the power distribution system reliability wherein the reliability is measured as a probability of the system functionality at a first time that is greater than or equal to the system functionality at a second time wherein the first time is later than the second time.
 24. A computer system in accordance with claim 22 further configured to select a configuration that facilitates optimizing the power distribution system availability wherein the availability is measured as a probability of the system functionality at any time is greater than or equal to a predetermined system functionality goal.
 25. A computer system in accordance with claim 19 configured to determine a plurality of alternative configurations of the power distribution system based on varying a number of components in a redundant scheme for each alternative configuration.
 26. A computer system in accordance with claim 19 further configured to: receive a set of parameters describing a plurality components of the power distribution system; vary a redundancy of the plurality components for the received set of parameters; and determine a power distribution system reliability and system availability for each level of redundancy.
 27. A computer system in accordance with claim 26 configured to vary a redundancy of said plurality of components wherein the plurality of components comprises at least one of a central control processing unit (CCPU), a CCPU communications interface, a digital communications network, an Ethernet switch, a node electronics unit (NEU), an uninterruptible power supply (UPS), a main power supply to the UPS, a communications connection, and a circuit breaker.
 28. A computer system in accordance with claim 26 further configured to: evaluate at least one of a life cycle cost, a system availability, and a system reliability for each level of redundancy; and determine a level of redundancy to facilitate optimizing the power distribution system life-cycle cost, reliability, and availability.
 29. A computer system in accordance with claim 26 configured to receive a set of parameters that includes at least one of a number of available power sources, a reliability of available power sources, a number of branch circuits, a configuration of branch circuits, a number of a plurality of loads, and a rating of a plurality of loads.
 30. A computer system in accordance with claim 26 further configured to: determine a user's power distribution system reliability goal; determine a reliability of each available control power supply; determine a reliability of a plurality of combinations of each available control power supply; and compare the reliability of each combination of available power supplies to the determined reliability goal.
 31. A computer system in accordance with claim 19 wherein the power distribution system includes at least one circuit breaker, each circuit breaker supplying a load with electrical power from at least one electrical source, the circuit breakers configured in a hierarchical format from load to source, said method further configured to: detect a circuit breaker error associated with a first circuit breaker that prevents the first circuit breaker from interrupting a flow of load current; determine at least one alternate circuit breaker to interrupt the flow of load current; and adjust an operation of the determined at least one alternative circuit breaker.
 32. A computer system in accordance with claim 31 configured to modify a trip curve of the determined at least one alternative circuit breaker.
 33. A computer system in accordance with claim 31 configured to infer electrical parameters at the first circuit breaker based on electrical parameters sensed in the power distribution system.
 34. A computer system in accordance with claim 28 further configured to: determine a power distribution system software configuration corresponding to the determined level of redundancy; determine a cost of implementing the power distribution system software configuration; vary the determined level of redundancy; and determine the power distribution system software configuration that facilitates optimizing the power distribution system cost.
 35. A computer system in accordance with claim 34 configured to determine a cost of implementing the power distribution system software configuration wherein cost includes at least one of a production schedule cost, a resource cost, and a labor cost.
 36. A computer system in accordance with claim 34 configured to determine the power distribution system software configuration that facilitates optimizing the power distribution system cost wherein said power distribution system cost includes at least one of a production schedule cost, a resource cost, a labor cost, a reliability cost, and an availability cost. 